In 2016.00, the thermal expansion of water was contributing to the thermal strain of the soil body, which is incorrect: the displacements are only governed by the thermal expansion of the soil skeleton. The thermal expansion of liquid water plays a role in excess pore pressures and groundwater flow, but not directly in the displacements.
This issue with the thermal expansion is now solved in PLAXIS 2D 2016.01: the thermal expansion of the soil skeleton governs the thermal strain of the soil body.
If you are working with an older version, please update to the latest version.